Biological Productivity and
Coastal Habitats
• Why do we care?
– Fishing
– Water quality
– Wildlife
Ecology and Ecosystems
• Ecology
– Natural systems
– Include interactions between living and
non-living parts
• Ecosystem
– Totality of the environment
encompassing all chemical, physical,
geological and biological parts
• Food chain
– Succession of organisms within an
ecosystem base upon trophic dynamics
– Trophic dynamics
• Trophic refers to nutrition
• who is eaten by whom
Ecosystems
• Function by exchange of matter and
energy
• Differ in size, complexity, and
diversity of organisms
Ecosystem Energy Flow
• Plants take energy from the sun and
put it into the system
– Use chlorophyll in photosynthesis to
convert inorganic material into organic
compounds and to store energy for
growth and reproduction
– Plants are autotrophs
– Plants are primary producers
• Heterotrophs
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All other organisms
Consumers - animals
Decomposers – bacteria and fungi
Herbivores eat plants
Carnivores eat animals
Omnivores eat both plants and animals
Ecosystem Pathway
•Material is constantly cycled
•Energy comes from sun, gradually
dissipates as heat and is lost
Trophic Dynamics
• Trophic refers to nutrition
• Trophic dynamics - study of the
nutritional interconnections among
organisms within an ecosystem
Tropic Level
• Position of the organism within the
tropic dynamics
– Autotrophs – first level
• Provide the organic matter and energy for
all other levels
– Herbivores - second level
– Carnivores – third and higher levels
– Decomposers – the terminal level
Energy Pyramid
• Graphic representation of a food
chain in terms of the energy
contained at each trophic level
• The size of each successive level is
controlled by the size of the level
immediately below it
Primary Producers
• Phytoplankton in the ocean
• Require sunlight, nutrients, water
and carbon dioxide for
photosynthesis
• The limiting factors is commonly
sunlight and/or nutrients
• Photosynthesis
Sunlight + 6CO2 +6 H2O ? C6H12O6 + 6O2
– C6H12O6 is sugar
• Other organic compounds besides
sugar, such as RMA and DNA, are
also formed
• Rapid cell division
• Phytoplankton blooms – rapid
expansion of a phytoplankton
population because light and
nutrients are abundant
Doubling Rates
• Someone will start working for a
penny a day, but the rate doubles
every day for 30 days. Has to last 30
days.
• Is that a good deal for the employer
or employee?
Consumers
• Animals are the consumers
• Animals break down the organic
compounds into their inorganic
components to obtain the stored
energy
• Respiration
C6H12O6 + 6O2 ? 6CO2 +6 H2O + energy
• The recovered energy is used for
movement, reproduction and growth
• Food consumed by most organisms
is proportional to their body size
– Generally smaller animals eat smaller
food and larger animals larger food
Feeding Styles
• Grazers – consume plant material –
copepods, snails, sea urchins, some
fish
• Predators – hunt and kill prey –
sharks, some fish
• Scavengers – consume dead organic
matter – crabs, lobsters, snails, some
fish
• Filter feeders – filter the water for
suspended food – barnacles,
mussels, oysters
• Deposit feeders – selectively or notselectively consume food that is
mixed in the sediments
What Feeding Style are
These Guys?
Population Size
• Dependent upon food supply
• Lag between the maximum
abundance of food and the maximum
population size
• Population goes in cycles
Decomposition
• Bacteria and fungi are the
decomposers
• They break down organic material
and release nutrients for recycling
• NH3 + 2O2 ? H+ +NO-3 + H2O
• Ammonia and oxygen to nitrate and water
• Nitrate is used by plants for growth
• Few bacteria are capable of completely
degrading organic material into its
inorganic components
• Most operate in succession with other
bacteria to decompose material in a series
of stages
• Bacteria are food for other organisms
either directly or indirectly
Bacteria
• Aerobic
– require free oxygen to respire and
decompose dead matter
• Anaerobic
– Live in an oxygen free (anoxic)
environment
– Obtain oxygen for respiration from
other sources such as SO4-2 (sulfate ion)
and release H2S (hydrogen sulfide gas)
as a byproduct of decay
– Hydrogen sulfide – rotten egg smell
Bacteria
• Most are heterotrophs
• Two autotrophic bacteria
– Cyanobacteria
• blue-green algae
• Photosynthesize
– Chemosynthetic bacteria
• Use chemical energy released in the
oxidation of inorganic compounds to
produce food
• Volcanic vent communities
The System
Food Chains
• Transfer the energy from one tropic
level to another
• Biomass is the quantity of living
matter per volume of water
• With each higher trophic level, the
size of the organisms generally
increase, but their number and total
biomass decreases
• Rate of growth is inversely related to
position in the food chain
• Low on the food chain, the
individuals are small but reproduce
rapidly
• High on the food chain, individuals
are large but reproduce slowly
Two Major Food Chains
• Grazing food chain
– Phytoplankton ? zooplankton ?
nekton
– Herbivores consume autotrophs in the
photic zone
• Detritus food chain
– Detritus ? deposit feeder ? nekton
– Non-living wastes form the base of the
food chain
– Organic matter from the surface waters
settles into the deep-sea food chain
when it is consumed by detritus feeders
Energy Transfer
• Only about 10-20% of the energy is
transferred between trophic levels
• This produces a rapid decline in
biomass at each successive trophic
level
Efficiency
• Example of 10% efficiency
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100,000,000 g diatoms
10,000,000 g copepods
1,000,000 g small fish
100,000 g large fish
10,000 g human = 10 kg = 22 lb
• Most (80-90%) of the energy consumed by
organisms is lost in movement or in
growing non-nutritional structures, such as
bone or shell
• The longer the food chain, the greater the
autotrophic biomass needed to support it
• There must be a balance between the
energy expended to obtain food and the
energy obtained from the food
• Not all potential food sources are practical
Solar Radiation
• Only 0.1-0.2% of the solar radiation
is employed for photosynthesis and
its energy is stored in organic
compound
• The amount of light decreases
rapidly with depth
Primary Production
• Net primary production is the
amount of carbon converted into
organic material above that required
for the minimal survival of the
autotrophy
• The amount of organic material
available for growth and
reproduction
• Compensation depth – depth where
net primary production equals zero
– Not the CCD
– Usually located where light intensity is
about 1% of the surface value and
typically occurs at a depth of~110 m in
clear ocean water or 15 m in estuaries
Primary Production
• Most of the light entering the ocean
is converted into heat
– Productivity is small below 0oC and
above 40oC, but between these
productivity increases with temperature
• Despite decreasing solar radiation,
growth and reproduction
productivity tends to increase
poleward because of greater
availability of nutrients away from
the equator
Nutrients
• Nutrients are chemicals needed for
survival, growth, and reproduction
• Macronutrients are elements or
compounds required in large
quantities and include phosphorus
(P), nitrogen (N), and silicon (Si)
– Scarcity of macronutrients usually
occurs over a broad region and limits
growth on a regional scale
• Micronutrients are indispensable
elements and compounds used in
very small quantities
– Iron, copper, manganese, boron, cobalt
– trace metals
– Because they are needed in small
amounts, they rarely are scarce over a
large region, but may limit growth
locally
Nutrient Limitations
• Phytoplankton generally requires
phosphorus, nitrogen and carbon in
the ratio of 116 C: 16N : 1P
• Despite the enormous demand for
carbon, it is so abundant as
bicarbonate ion that it is never a
limiting factor
• N and P are needed in much smaller
amounts, but can be limiting factors
• N harder to recycle than P
– Decomposition releases N compounds
more slowly than P
– N is usually the limiting factor
• Silicon can be a limiting factor for
diatoms and silicoflagellates
Vertical Limitations
• Dead organisms sink into deep water
removing them from the productive
surface zone – photic zone
• Upwelling and turbulence can return
nutrients to the surface
• Upwelling regions are highly
productive
• Upwelling occurs
– Coastal waters
– Along the equator between the large
circulation gyres
• Near shore turbulence
– From tides, waves, and storms (waves)
Other Limitations
• Overgrazing of autotrophs can
deplete the population and lead to a
decrease in productivity
• Turbidity reduces the depth of light
penetration and restricts productivity
even when nutrients are abundant
Marine Productivity
• Primary production – the total
amount of carbon in grams
converted into organic material per
square meter of sea surface per year
• If plants abound, so will animals
• Factors that limit plant growth and
reduce primary productivity include:
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Solar radiation - primary
Nutrients- primary
Upwelling- primary
Turbulence - secondary
Grazing intensity - secondary
Turbidity - secondary
Productivity Variation
• Productivity varies greatly in
different parts of the ocean in
response to the availability of
nutrients and sunlight
– Photic zone are the only regions
capable of supporting life
– Deep sea vents are one exception
Productivity by latitude
regions
• In tropics and subtropics
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Light is abundant
Nutrients are limiting
Strong thermocline restricts upwelling
Result = low productivity most places
High productivity where upwelling
occurs
• In temperate regions
– Productivity is seasonal
– Sunlight is limited seasonally
– Nutrients also vary seasonally
• In polar regions
– Nutrient rich
– Light poor
Temperate Zone Limitations
• In the winter
– the water column is isothermal and
mixes easily
– Nutrients are abundant
– Sunlight restricts productivity
• In the Spring
– Sunlight becomes more abundant
– Diatoms and phytoplankton bloom
• In the Summer
– Productivity declines as:
• Thermocline develops and prevents vertical
mixing and resupply of nutrients
• Usage depletes the available nutrients
• Grazing by herbivores greatly reduces the
population of phytoplankton
• In the Fall
– Productivity initially increases as water
becomes isothermal and nutrients
become abundant
– Sunlight becomes limiting factor
Global Patterns of
Productivity
• Primary productivity varies from 25
to 1250 gm C/m 2/yr
– Lowest in the open ocean
• Low in center – like a desert
• High on edges
– Continental shelves – 50-200 gm
C/m2/yr
– Highest in estuaries, upwelling areas
– High in polar regions
Estimating Productivity
• Plankton biomass is good indicator
of biomass in rest of food web
• Annual primary production =APP
– APP = PPR x Area
– PPR – Primary production rate
• Transfer efficiency = TE
– Measure of the amount of carbon that is
passed between trophic levels
– Varies from 10-20 %, generally
• Potential production = PP
– PP for each trophic level
– PP = APP x TE (for each step)
– Must use TE for each step in the food
chain to the trophic level of the
organism under consideration
Fish Production
Productivity
• Open ocean has greatest biomass
productivity
– Rate of productivity is very low
– Area is very large
• Open ocean food chains are longer
and energy transfer low, so fish
populations are small
• Most fish production is equally
divided between upwelling areas and
coastal waters
• Annual fish production
– ~ 240 million tons/yr
Fishing
• Annual fish production
– ~ 240 million tons/yr
• Fishing
– 1970 – 70 million tons/yr
– 1990 – 98 million tons/yr
– Limit should be 110 million tons/yr
Productivity in Upwelling
Regions
• Upwelling of nutrient rich water
supports large populations of
phytoplankton and fish
• Waters off Peru – upwelling and
support one of the world’s largest
fisheries
• During El Nino, the upwelling stops
and the productivity is severely
reduced
• Leads to mass starvation of
organisms – fish, birds, etc.
Global Primary Productivity
Global Zooplankton Density
Global Benthic Biomass
Density
Residence Time
• The average time that a material
remains in a system
• Calculations are only valid if input
and output of material from system
are known
• If the system is steady-state, input =
output
Residence time = material within the system
input or output of system